The nurse is teaching a class on muscular coordination and explains it is the movement of what electrolyte that contributes to the process of muscle contraction and relaxation?

Choice A rationale

Myasthenia gravis primarily affects voluntary muscles, especially those involved in breathing and facial movements. Gastrointestinal (GI) and lower extremity muscles are generally not the main muscles affected by this condition. It is an autoimmune disorder that impacts the neuromuscular junction, where nerves communicate with muscles, leading to muscle weakness and fatigue.

Choice B rationale

The central nervous system (CNS), memory, and cognition are not typically impacted by myasthenia gravis. This disorder primarily involves peripheral nervous system issues that affect voluntary muscle control rather than cognitive functions. Myasthenia gravis does not cause alterations in memory or cognition as seen with central nervous system disorders like Alzheimer's disease.

Choice C rationale

Myasthenia gravis notably affects respiratory and facial muscles. The autoimmune attack on acetylcholine receptors leads to muscle weakness, particularly in muscles controlling eye movements, facial expressions, and breathing. Patients may experience difficulty breathing, swallowing, and maintaining an open airway due to this muscle weakness.

Choice D rationale

The cardiovascular system and postural muscles are not commonly affected by myasthenia gravis. This condition involves the neuromuscular junction and leads to fatigue in voluntary muscles, primarily those involved in eye movement, facial expressions, and respiration. Cardiovascular symptoms are not a direct consequence of myasthenia gravis.

Choice A rationale

This choice is incorrect. A complete occlusion of a coronary vessel results in a myocardial infarction (heart attack), not unstable angina. Unstable angina occurs when there is a significant narrowing or partial blockage of a coronary artery, leading to reduced blood flow and oxygen supply to the heart muscle, causing pain or discomfort. Complete occlusion would cause permanent damage to the heart muscle, which is not the case with unstable angina.

Choice B rationale

This choice is correct. While unstable angina is mainly caused by narrowing of the coronary arteries, it can also be caused by a spasm of the blood vessel. This spasm, also known as vasospasm, reduces the amount of blood flow to the heart muscle, resulting in pain. These spasms can occur even if the coronary arteries do not have significant plaque buildup, adding another layer of complexity to the condition.

Choice C rationale

This choice is partially correct. The body’s response to a lack of oxygen (ischemia) in the heart muscle does result in pain, known as angina. However, this choice does not fully capture the specific nature of unstable angina, which involves episodes of pain that occur more frequently and are more severe than those associated with stable angina, and can occur at rest or with minimal exertion, indicating a higher risk for a heart attack.

Choice D rationale

This choice is correct. Unstable angina is characterized by a serious narrowing of a coronary artery that reduces oxygen supply to the heart. This narrowing is typically due to atherosclerotic plaque and can be complicated by blood clots or spasms. Unlike stable angina, the pain of unstable angina is more unpredictable and can occur without a triggering factor like exercise or stress, signaling a higher risk of a heart attack.